LGA 1356 is one of the two sockets designed as a replacement for the LGA 1366 CPU socket, the other being LGA 2011 (which is known as Socket R). LGA 1356 has 1356 protruding pins to make contact with the pads on the processor. Processors of LGA 1356 and LGA 1366 sockets are not compatible with each other since they have different socket notches. It supports Intel Sandy Bridge-E microprocessors, codenamed Romley-EN, marketed under the Xeon-E5 2400 series.
The main difference between LGA 2011 and LGA 1356 is 2 Intel QuickPath Interconnect (QPI)s connections on the LGA 2011 and 1 QPI connection on the LGA 1356. Other noticeable differences include 24 lanes of PCI Express (PCI-e) version 3.0 connections compared to 40 lanes on the LGA 2011, and three channels of DDR3 support compared to four on the LGA 2011. Each DDR3 channel can support one more DIMM (only applicable to DDR3 and not DDR3-L).
Plans were leaked in early 2011, with estimated releases in the first quarter of 2012. In September 2011, releases were estimated to be at the end of the first quarter of 2012.